Simple, inexpensive measures to cut emissions of two common pollutants will slow global warming, save millions of lives and boost crop production around the world, a large international team of scientists reported Thursday.
The climate change debate has centered on carbon dioxide, a gas that wafts in the atmosphere for decades, trapping heat. But in recent years, scientists have pointed to two other, shorter-term pollutants -- methane and soot, also known as black carbon -- that also drive climate change.
Slashing emissions of these twin threats would be a "win-win-win" for climate, human health and agriculture, said NASA climate scientist Drew Shindell, who led the study appearing in the journal Science. "Even if you don't believe climate change is a problem, these things are worth doing."
Reducing methane and soot would slow global warming dramatically -- by almost a degree Fahrenheit -- by the middle of the century, according to computer simulations run by the 24-member international team.
At the same time, the simulations show that such actions would save 700,000 to 4.7 million lives annually, as better air quality would prevent lung and cardiovascular diseases.
Global crop yields also would rise, by 30 to 135 metric tons annually, as rice, corn, wheat and soybean plants would have an easier time absorbing the nutrients they need from the air, according to the report.
"In the absence of a global carbon dioxide agreement, it makes sense to move ahead on global efforts to reduce these other gases," said Joyce Penner of the University of Michigan, who has studied the climate impacts of soot.
Previous studies have noted the benefits of reducing methane and soot. But the new study looked at the specific impact of about 400 measures policymakers could take. Of those, just 14 interventions -- such as eliminating wood-burning stoves, dampening emissions from diesel vehicles and capturing methane released from coal mines -- would offer big benefits. "They're all things we know how to do, and have done; we just haven't done them worldwide," said Shindell, who works at the NASA Goddard Institute for Space Studies in New York.
About 3 billion people in the developing world rely on stoves that burn wood, dung and other fuels that throw off soot. Switching to cleaner-burning stoves would help reduce short-term global warming while quickly improving local air quality.